Polymer-based heat transfer device and process for manufacturing the same

ABSTRACT

A polymer-based heat transfer device comprising a polymer-based housing having housing walls defining a working fluid chamber, a porous structure extending in the working fluid chamber from at least one of the two opposed ones of the housing walls, and a plurality of housing wall spacers, such as support posts, extending between the two housing walls to maintain the two housing walls in a spaced-apart configuration with the working fluid chamber extending in between is provided. Also described is a polymer-based heat transfer device comprising a polymer-based housing having housing walls defining a working fluid chamber and a porous structure extending in the working fluid chamber from at least one of the two opposed ones of the housing walls, and heat-conductive metal or ceramic-based foam contacting at least one of the housing walls. A process for manufacturing the polymer-based heat transfer device is provided.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims priority under 35 USC § 119(e) of U.S.provisional patent application 62/500,657 filed on May 3, 2017, thespecification of which is hereby incorporated by reference.

TECHNICAL FIELD

The technical field generally relates to heat transfer devices forextracting heat from a heat source with a working fluid. Moreparticularly, the technical field relates to a polymer-based heattransfer device containing an internal working fluid, such as a heatpipe, a cold plate and a vapor chamber. It also relates to a process formanufacturing a polymer-based heat transfer device, such as a heat pipe,a cold plate and a vapor chamber.

BACKGROUND

Traditionally, high thermal conductivity metals such as copper andaluminium are used for heat transfer device fabrication, such as heatpipes, cold plates and vapor chambers. However, metal-based heat pipesare relatively expensive due to the material and manufacturing costs.Furthermore, they provide less freedom for design purposes. Typically,only cylindrical and rectangular designs can be manufactured.

There is thus a need for heat transfer devices having lowermanufacturing and/or material costs and which could provide moreflexibility for shape design. In view of the above, there is a need forheat transfer devices which would be able to overcome, or at leastminimize, some of the above-discussed prior art concerns.

SUMMARY

According to a general aspect, there is provided a polymer-based heattransfer device. The polymer-based heat pipe comprises a polymer-basedhousing. The polymer-based housing has housing walls with an innersurface defining a working fluid chamber and a porous structureextending in the working fluid chamber from at least one of the housingwalls, and a plurality of housing wall spacers, such as support posts,extending between two opposed ones of the housing walls to maintain thetwo opposed ones of the housing walls in a spaced-apart configurationwith the working fluid chamber extending in between.

In an embodiment, the polymer-based housing comprises a first housingshell and a second housing shell superposed to one another and sealedtogether.

In an embodiment, the plurality of housing wall spacers comprises aplurality of spaced-apart support posts protruding from the innersurface of one of the housing walls towards the opposed one of thehousing walls and contacting same.

In an embodiment, the polymer-based housing comprises a plurality ofspaced-apart ridges protruding from at least one of the housing wallsand extending substantially parallel to one another and defininginbetween a plurality of microchannels. In an embodiment, the pluralityof housing wall spacers comprises the ridges which extend towards theopposed one of the housing walls and contact same.

According to another general aspect, there is provided a polymer-basedheat transfer device. The polymer-based heat transfer device comprises apolymer-based housing and heat-conductive metal-based foam. Thepolymer-based housing has housing walls defining a working fluid chamberand a porous structure extending in the working fluid chamber from atleast one of the housing walls. The heat-conductive metal-based foamcontacts the at least one of the housing walls.

In an embodiment, the heat-conductive metal-based foam at leastpartially extends in the working fluid chamber to define the porousstructure.

In an embodiment, the heat-conductive metal-based foam is at leastpartially embedded in the at least one of the two opposed ones of thehousing walls.

In an embodiment, the porous structure comprises a plurality ofmicrochannels defined in the at least one of the two opposed ones of thehousing walls.

According to a further general aspect, there is provided a process formanufacturing a polymer-based heat transfer device. The processcomprises steps of forming a first polymer-based housing shell and asecond polymer-based housing shell, at least one of the polymer-basedhousing shells having a porous structure on at least one inner surfacethereof; superposing the first housing shell and the second housingshell with one of the inner surfaces facing another one of the innersurfaces and being spaced-apart to define a working fluid chamberinbetween; at least partially peripherally sealing the first housingshell and the second housing shell together; and inserting a workingfluid inside the working fluid chamber.

According to another general aspect, there is provided a polymer-basedheat transfer device. The polymer-based heat transfer device comprises:a polymer-based housing having housing walls with an inner surfacedefining a working fluid chamber, a porous structure extending in theworking fluid chamber from at least one of the housing walls, and aplurality of housing wall spacers extending between two opposed ones ofthe housing walls to maintain the two opposed ones of the housing wallsin a spaced-apart configuration with the working fluid chamber extendingin between.

In an embodiment, the polymer-based housing comprises a first housingshell and a second housing shell superposed to one another and sealedtogether.

In an embodiment, the plurality of housing wall spacers comprises aplurality of spaced-apart support posts protruding from the innersurface of one of the housing walls towards an opposed one of thehousing walls and contacting same.

In an embodiment, the porous structure comprises a plurality ofspaced-apart ridges protruding from at least one of the housing wallsand extending substantially parallel to one another and defininginbetween a plurality of microchannels. The plurality of housing wallspacers can comprise the ridges which extend towards an opposed one ofthe housing walls and contact same. The ridges can be polymer-basedridges. The microchannels can have a width and a length ranging betweenabout 100 and about 1000 μm and an aspect ratio (depth/width) betweenabout 0.1 mm and about 10 mm. A bottom surface of the microchannels canbe hydrophilic and a top surface of the microchannels can behydrophobic.

In an embodiment, the housing walls have a thickness ranging betweenabout 0.1 mm and about 5 mm.

In an embodiment, the housing wall spacers comprise a plurality ofspaced-apart posts having a diameter ranging between about 0.1 mm andabout 10 mm.

In an embodiment, the working fluid chamber has a height ranging betweenabout 0.25 mm and about 5 mm.

In an embodiment, the polymer-based heat transfer device is a heat pipeand the working fluid chamber is a closed working fluid chamber.

In an embodiment, the polymer-based heat transfer device is a cold plateand the polymer-based housing comprises a working fluid inlet port and aworking fluid outlet port, spaced-apart from the working fluid inletport.

In an embodiment, the polymer-based housing comprises at least oneheat-conductive insert embedded within at least one of the housingwalls. The at least one heat-conductive insert can comprise aheat-conductive metal-based foam entirely embedded in the at least oneof the housing walls and the porous structure can comprise a pluralityof spaced-apart ridges protruding from at least one of the housing wallsand extending substantially parallel to one another and defininginbetween a plurality of microchannels.

In an embodiment, the polymer-based housing is polyethylene-based.

In an embodiment, the polymer-based heat transfer device furthercomprises a high barrier coating, such as indium tin oxide (ITO),applied onto at least one of the inner surface of the housing walls andan outer surface of the housing walls. The polymer-based heat transferdevice can further comprise an aluminium oxide layer. The polymer-basedheat transfer device can further comprise a protective layer comprisingat least one of SiO and SiON_(x) or at least one of an electroplatedcopper thin layer and an electroplated chrome thin layer. The protectivelayer can be applied onto the inner surfaces of the housing walls.

In an embodiment, the inner surfaces of the housing walls areplasma-treated.

According to still another general aspect, there is provided apolymer-based heat transfer device comprising: a polymer-based housinghaving housing walls defining a working fluid chamber and a porousstructure extending in the working fluid chamber from at least one ofthe housing walls; and a heat-conductive metal-based foam contacting theat least one of the housing walls.

In an embodiment, the heat-conductive metal-based foam at leastpartially extends in the working fluid chamber to define the porousstructure.

In an embodiment, the heat-conductive metal-based foam is at leastpartially embedded in the at least one of the housing walls.

In an embodiment, the heat-conductive metal-based foam is entirelyembedded in the at least one of the housing walls. The polymer-basedhousing can further comprise a plurality of housing wall spacersincluding a plurality of spaced-apart support posts protruding from aninner surface of one of the housing walls towards an opposed one of thehousing walls and contacting same. The porous structure can comprise aplurality of spaced-apart ridges protruding from at least one of thehousing walls and extending substantially parallel to one another anddefining inbetween a plurality of microchannels. The ridges can extendtowards an opposed one of the housing walls and contact same to definehousing wall spacers. The ridges can be polymer-based ridges. Themicrochannels can have a width and a length ranging between about 100and about 1000 μm and an aspect ratio (depth/width) between about 0.1 mmand about 10 mm. A bottom surface of the microchannels can behydrophilic and a top surface of the microchannels can be hydrophobic.

In an embodiment, the porous structure comprises a plurality ofmicrochannels defined formed superficially on in the at least one of thetwo opposed ones of the housing walls.

In an embodiment, the polymer-based housing comprises a first housingshell and a second housing shell superposed to one another and sealedtogether.

In an embodiment, the housing walls have a thickness ranging betweenabout 0.1 mm and about 5 mm.

In an embodiment, the working fluid chamber has a height ranging betweenabout 0.25 mm and about 5 mm.

In an embodiment, the polymer-based heat transfer device is a heat pipeand the working fluid chamber is a closed working fluid chamber.

In an embodiment, the polymer-based heat transfer device is a cold plateand the polymer-based housing comprises a working fluid inlet port and aworking fluid outlet port, spaced-apart from the working fluid inletport.

In an embodiment, the polymer-based housing comprises at least oneheat-conductive insert embedded within at least one of the housingwalls.

In an embodiment, the polymer-based housing is polyethylene-based.

In an embodiment, the polymer-based heat transfer device furthercomprises a high barrier coating, such as indium tin oxide (ITO),applied onto at least one of an inner surface of the housing walls andan outer surface of the housing walls. The polymer-based heat transferdevice can further comprise an aluminium oxide layer. The polymer-basedheat transfer device can further comprise a protective layer comprisingat least one of SiO and SiON_(x) or a protective layer comprising atleast one of an electroplated copper thin layer and an electroplatedchrome thin layer. The protective layer can applied onto inner surfacesof the housing walls.

In an embodiment, the inner surfaces of the housing walls areplasma-treated.

According to still a further general aspect, there is provided a processfor manufacturing a polymer-based heat transfer device. The processcomprises: forming a first polymer-based housing shell and a secondpolymer-based housing shell, at least one of the polymer-based housingshells having a porous structure on at least one inner surface thereof;superposing the first housing shell and the second housing shell withthe inner surfaces facing another one of the inner surfaces and beingspaced-apart to define a working fluid chamber inbetween; at leastpartially peripherally sealing the first housing shell and the secondhousing shells together; and inserting a working fluid inside theworking fluid chamber.

In an embodiment, forming the first polymer-based housing shell and thesecond polymer-based housing shell comprises forming a plurality ofhousing wall spacers on an inner surface of at least one of the firstand the second polymer-based housing shells, the housing wall spacersbeing configured to contact an opposed one of the inner surface when thefirst and the second polymer-based housing shells are superposed.

In an embodiment, forming the first polymer-based housing shell and thesecond polymer-based housing shell comprises forming a plurality ofspaced-apart ridges protruding from an inner surface of at least one ofthe housing shells and extending substantially parallel to one anotherand defining inbetween a plurality of microchannels.

In an embodiment, the process further comprises performing at least oneof an hydrophilic treatment on a bottom surface of the microchannels andan hydrophobic treatment on a top surface of the microchannels.

In an embodiment, forming the first polymer-based housing shell and thesecond polymer-based housing shell comprises embedding at least oneheat-conductive insert within at least one of the first and the secondpolymer-based housing shells.

In an embodiment, embedding the at least one heat-conductive insertwithin at least one of the first and the second polymer-based housingshells comprises placing the heat-conductive insert inside a shell moldand injecting polymer inside the shell mold to at least partially embedthe at least one heat-conductive insert inside the injected polymer.

In an embodiment, the process further comprises applying a high barriercoating onto at least one of an inner surface and an outer surface ofthe first and the second polymer-based housing shells.

In an embodiment, the process further comprises applying an aluminiumoxide layer onto the high barrier coating.

In an embodiment, the process further comprises electroplating a thinlayer of copper or chrome onto at least one of inner surfaces of thefirst and the second polymer-based housing shells.

In an embodiment, the process further comprises plasma-treating innersurfaces of the first and the second polymer-based housing shells.

In an embodiment, the process further comprises at least partiallyperipherally sealing the first housing shell and the second housingshell together comprises plastic welding or sealing through vacuum epoxythe first housing shell and the second housing shell together.

Other features and advantages of the invention will be better understoodupon reading of embodiments thereof with reference to the appendeddrawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic sectional representation of a polymer-based heattransfer device and, more particularly, a heat pipe in operationaccording to an embodiment.

FIG. 2 is a schematic sectional view of a polymer-based heat transferdevice, and more particularly, a heat pipe according to a possibleembodiment wherein inner surfaces of a polymer-based housing include awicking structure as a porous structure.

FIG. 3 is a schematic top perspective view, sectioned, of thepolymer-based heat pipe shown in FIG. 2.

FIG. 4 is a schematic top perspective view of a housing shell of apolymer-based heat pipe according to another possible embodiment,including a plurality of spaced-apart support posts configured toprotrude from an inner surface of the housing shell and in a workingfluid chamber of the polymer-based heat pipe.

FIG. 5 is a top perspective view, enlarged, of a section of the housingshell of the polymer-based heat pipe shown in FIG. 4.

FIG. 6 is an exploded top perspective view of the polymer-based heatpipe including the housing shell shown in FIG. 4.

FIG. 7 is a photograph of a section of the housing shell fabricated inaccordance with the embodiment shown in FIG. 4.

FIG. 8 is a microscopic view of a wicking structure of a polymer-basedheat pipe fabricated in accordance with the embodiment shown in FIG. 2.

FIG. 9 is a photograph showing a top view of a polymer-based heattransfer device and, more particularly, a heat pipe according to apossible embodiment.

FIG. 10 is a schematic sectional view of a section of a housing wall ofa polymer-based heat transfer device and, more particularly, a heat pipeaccording to another possible embodiment, with heat-conductivemetal-based foam embedded in the housing wall.

FIG. 11 is a schematic sectional view of a polymer-based heat pipeincluding the housing wall shown in FIG. 10, in accordance with anembodiment.

FIG. 12 is a schematic sectional view of a section of a housing wall ofa polymer-based heat transfer device and, more particularly, a heat pipeaccording to a possible embodiment, with heat-conductive metal-basedfoam partially embedded in the housing wall and partially extendingoutwardly from the housing wall.

FIG. 13 is a schematic diagram sectional view of a polymer-based heatpipe including the housing wall shown in FIG. 12, in accordance with anembodiment.

FIG. 14 is a microscopic side view, enlarged, of the housing wall of aheat pipe fabricated in accordance with the embodiment shown in FIG. 12.

FIG. 15 is a microscopic top view, enlarged, of the housing wall of theheat pipe fabricated in accordance with the embodiment shown in FIG. 12.

FIG. 16 is a schematic sectional view of a polymer-based heat transferdevice, and more particularly, a cold plate according to a possibleembodiment wherein an inner surface of a polymer-based housing includesa conductive wall insert and a grooved structure as a porous structure.

FIG. 17 is a schematic sectional view of a cold plate according toanother possible embodiment wherein an inner surface of a polymer-basedhousing includes a conductive porous medium as a porous structure.

FIG. 18 is a microscopic top view, enlarged, of a polymeric surfacecovered by an impermeable metal-based layer according to a possibleembodiment.

FIG. 19 is a graph showing effect of an oxygen plasma treatment on awater contact angle for a polymeric surface.

FIG. 20 is a photograph showing a charging station for a polymer-basedheat pipe according to a possible embodiment.

FIG. 21 is a schematic representation of an application of apolymer-based heat transfer device for electric and hybrid vehicles,according to a possible embodiment.

FIG. 22 is a schematic representation of an application of apolymer-based heat transfer device for prosthesis systems, according toa possible embodiment.

DETAILED DESCRIPTION

In the following description, similar features in the drawings have beengiven similar reference numerals. In order to not unduly encumber thefigures, some elements may not be indicated on some figures if they werealready mentioned in preceding figures. It should also be understoodherein that the elements of the drawings are not necessarily drawn toscale, and that the emphasis is instead being placed on clearlyillustrating the elements and structures of the present embodiments.

Moreover, it will be appreciated that positional descriptions such as“top”, “bottom”, “under”, “left”, “right”, “front”, “rear”, “adjacent”and “opposite” and the like should, unless otherwise indicated, be takenin the context of the figures and should not be considered limiting.

Furthermore, it is to be understood that the invention can be carriedout or practiced in various ways and that the invention can beimplemented in embodiments other than the ones outlined in thedescription above.

It is to be understood that, where the claims or specification refer to“a” or “an” element, such reference is not be construed that there isonly one of that element.

It is to be understood that, where the specification states that acomponent, feature, structure, or characteristic “may”, “might”, “can”or “could” be included, that particular component, feature, structure,or characteristic is not required to be included.

Any publications, including patents, patent applications and articles,referenced or mentioned in this specification are herein incorporated intheir entirety into the specification, to the same extent as if eachindividual publication was specifically and individually indicated to beincorporated herein. In addition, citation or identification of anyreference in the description of some embodiments of the invention shallnot be construed as an admission that such reference is available asprior art to the present invention.

Generally described, the present disclosure concerns heat transferdevices such as heat pipes, cold plates, and vapor chambers forextracting heat from a heat source with a working fluid, as well as aprocess for manufacturing the heat transfer devices, such as heat pipes,cold plates, and vapor chambers. The heat transfer device is of the typeof polymer-based heat transfer device comprising relative low thermalconductivity (in comparison to metal-based heat transfer device). Moreparticularly, a housing of the heat transfer device is mainlyconstructed of plastics, such as low cost commercially availablepolymers, including high-density polyethylene (HDPE). Since polymers aretypically cheaper than metal, this type of polymer-based heat pipe maybe useful, for example, for less thermally intensive applications,wherein low manufacturing costs are non-negligible and/or relativelylow-weight heat transfer devices are suitable.

Broadly described, the polymer-based heat transfer device (hereinafterreferred to as “heat transfer device” unless specified otherwise)includes a working fluid chamber of a relatively small height at leastpartially delimited by a porous structure fabricated, formed or added onan inner surface of at least one housing wall of the heat transferdevice. The working fluid chamber, which can be a closed working fluidchamber, including an at least partially empty space defined by theporous structure, is typically filled (or at least partially filled)with a working fluid, such as water.

An implementation of the polymer-based heat transfer device will bedescribed in reference to FIG. 1 showing a heat pipe, as heat transferdevice. In FIG. 1, showing the heat pipe in operation, one end or sideof the polymer-based heat transfer device and, more particularly, a heatpipe, is placed close to a heat source, while another end or side of thepolymer-based heat pipe is configured as a heat sink for heat rejection.In a vapor chamber configuration, the heat source is located across anarea on one of the walls, while the heat sink is located elsewhere onthe same wall or on the opposite wall. Evaporation and condensationoccur at the areas located close to the heat source and the heat sink,respectively. After evaporation of the working fluid from one end, theworking fluid, in its vapour phase, flows within the working fluidchamber towards the heat sink, where its condenses back to its originalliquid phase. After its evaporation, the evaporated fluid leaves anempty space behind that is to be filled with the working fluid remainingin the porous structure by capillarity.

The polymer-based housing has housing walls with an inner surfacedefining a working fluid chamber. The polymer-based housing includes aporous structure provided on at least one of two opposed ones of thehousing walls and extending in the working fluid chamber. The porousstructure includes a structure having channels through which a fluid canflow. It can include a porous structure having small communicating poresdefining together channels through which the working fluid can flow,such as metallic foam structures, and/or a porous structure in whichelongated and substantially linear microchannels are defined eithersuperficially or internally.

In an implementation for a heat pipe, the porous structure comprises awicking structure. A wicking structure is a structure including ameniscus area in which a capillary pressure is develop at a liquid-vaporinterface in a manner such that the liquid can flow therein. In additionto being a porous structure, a wicking structure creates capillarypressure through the meniscus area.

According to one possible embodiment, the polymer-based housing may beformed from high density polyethylene (HDPE). Alternatively, thepolymer-based housing can be formed from polyethylene of differentdensity, crystal structure, molecular weight, and/or branching. Forexample, and without being limitative, the polymer-based housing can beformed from ultra-high-molecular-weight polyethylene,ultra-low-molecular-weight polyethylene, cross-linked polyethylene, orany other polyethylene-based material having the appropriate propertiesfor the targeted applications. It will be understood that thepolymer-based housing could also be formed from polymer, thermoplastic,acrylic, or any suitable materials having the required mechanical,electrical and/or thermal properties.

In an implementation, the polymer forming the polymer-based housing mayinclude a flame-retardant agent. In an embodiment, the flame-retardantagent can be combined with the polymer to provide an extra safety rolein case of fire. For instance, and without being limitative, anorganophosphorus-based flame retardant, such as triphenyl phosphate(TPP), can be combined with the polymer. For instance, during thermalrunaway of the lithium-ion battery, the polymer-based housing of theheat transfer device would melt due to increased temperature and theflame-retardant agent will be released, thus effectively suppressing thecombustion of the highly flammable electrolytes in the Li-ion battery.

In a non-limitative embodiment, the housing walls may have a thicknessranging from about 0.1 to about 5 mm and their inner surfaces may bespaced-apart from one another to define a working fluid chamber having aheight ranging between about 0.25 mm and about 5 mm. In accordance witha first aspect and referring to FIGS. 2 and 3, an embodiment of apolymer-based heat pipe 100 is shown.

The polymer-based heat pipe 100 comprises a polymer-based housing 110having housing walls 120 a, 120 b, 120 c and 120 d. The housing walls120 a, 120 b, 120 c and 120 d have an inner surface 121 defining aclosed working fluid chamber 130. In the illustrated variant, thepolymer-based housing 110 has a porous structure provided on two opposedones of the housing walls 120 a, 120 c. Alternatively, the polymer-basedhousing 110 can have a porous structure and, more particularly, awicking structure provided on at least one of the two opposed ones ofthe housing walls 120 a, 120 c. The porous structure 140 is located inthe closed working fluid chamber 130. In the embodiment shown in FIGS. 2and 3, the wicking structure 140 includes a plurality of elongatedridges 141 (or fins), extending substantially parallel to one anotherand protruding in the closed working fluid chamber 130 from the housingwalls 120 a, 120 c, and defining inbetween a plurality of microchannels142. In the embodiment shown, the ridges 141 and microchannels 142extend substantially linearly within the working fluid chamber 130. Theelongated ridges 141 and the microchannels 142 extend from anevaporation area to a condensation area of the polymer-based heat pipe100. The microchannels 142 define fluid paths between the evaporationarea to the condensation area in which may flow a working fluid 170,between the condensation area towards the evaporation area. Each one ofthe plurality of parallel microchannels 142 can have a predeterminedaspect ratio to determine a profile of the wicking structure 140. Theaspect ratio may be determined so as to provide a profile that may be,for example, and without being limitative, rectangular or square.Alternatively, the aspect ratio could be determined so as to obtain aparabolic, semicircular, U-shaped V-shaped profile. As it will beunderstood, the wicking structure 140 could be of any shape and ordimension, and may be, for example, channel-shaped and micrometric (witha dimension below about 1 mm). The wicking structure 140 can be formedof continuous ridges or discontinuous fins. The space between fins formsa two-dimensional array of interconnected m icrochannels.

In the embodiment shown in FIGS. 1 to 8, the wicking structure ispolymeric-based (or a polymeric wicking structure). However, as will bedescribed in more details below, in alternative embodiments, the wickingstructure can be metal-based. According to one possible embodiment, theporous structure 140 may be formed directly into the two opposed ones ofthe housing wall 120 a, 120 c. Alternatively, the porous structure 140could be progressively added (such as by additive manufacturing) ormounted onto the two opposed ones of the housing wall 120 a, 120 c. Themicrochannels 142 can be etched or machined on the inner surface 121 ofthe housing walls 120 a, 120 c to create an enhanced heat exchangesurface with the working fluid 170. In this case, the microchannels 142and the housing walls 120 a, 120 c are one single piece. In anembodiment, the housing walls can include a heat-conductive insertembedded therein and extending at least partially under themicrochannels 142, as will be described in more details below.

In the vapor chamber configuration, porous structures located on the twoopposed housing walls can be connected to allow liquid to move from onehousing wall to the other housing wall by capillarity. This capillaryconnection can be implemented on the other housing walls 120 b and 120d, or at other locations along the housing walls 120 a and 120 c.

According to one possible embodiment, the porous structure 140 maycomprise a plurality of microchannels of approximately 250 μm×300 μm(depth×width), corresponding to an aspect ratio (depth/width) ofapproximately 0.8. As it will be understood, dimensions of themicrochannels can be adjusted to the needs of one skilled in the art andso as to obtain an aspect ratio suitable for a given application. Forinstance, the dimensions of the microchannels may be comprised between100 and 1000 μm, and the aspect ratio (depth/width) may be comprisedbetween 0.1 to 10.

Referring to FIGS. 4 to 8, the polymer-based heat pipe 100 may furthercomprise a plurality of spaced-apart housing wall spacers embodied assupport posts 150 protruding from the inner surface 121 of at least oneof the housing wall 120 a, 120 c. The support posts 150 extend betweenthe two opposed ones of the housing walls 120 a, 120 c and providesupport to the polymer-based heat pipe 100, more particularly bymaintaining the two opposed ones of the housing walls 120 a, 120 c in aspaced-apart configuration to allow a flow of the working fluid 170 inthe closed working fluid chamber 130. Optionally, the plurality ofsupport posts 150 may be uniformly distributed across the surface of thetwo opposed ones of the housing walls 120 a, 120 c. Alternatively, theplurality of support posts 150 could be nonuniformly distributed acrossthe surface of the two opposed ones of the housing walls 120 a, 120 c,and could be, for example, found in greater density near the center, theperiphery and/or any other regions of the polymer-based heat pipe 100where a support post may be useful to increase resistance to pressuredifferences and external mechanical loads. Yet optionally, each one ofthe plurality of support posts 150 may have a right circular cylindricalbody. Alternatively, each one of the plurality of support posts 150could have a body of various geometrical configurations and could have acubic, parallelepipedal, pyramidal, or any other shapes useful to oneskilled in the art. Alternatively, the support posts can integratenarrow sections to act as a capillary path between opposed housing walls120 a and 120 c.

According to one possible embodiment, each of the support posts 150 hasa substantially circular cross-section and a diameter of about 1 mm. Itwill be understood that the shape and size may vary according to one'sneed. For example, the diameter of each of the support posts 150 may,for instance, and without being limitative, be comprised between about0.1 to about 10 mm.

In an alternative embodiment (not shown), the housing wall spacers canalso take an elongated shape, such as a wall or ridge.

As shown in FIGS. 3 and 6, according to one possible embodiment, thepolymer-based housing 110 may comprise a first housing shell 112 and asecond housing shell 114 superposed to one another and sealed together.Optionally, the polymer-based housing 110 may be formed of the first andsecond housing shells 112, 114, each defining an inner side 102 and anouter side 104 of the polymer-based heat pipe 100. Yet optionally, atleast one of the first and second housing shells 112, 114 may comprisethe porous structure 140 thereon. As shown in the embodiments of FIGS. 2to 8, both the first and second housing shells 112, 114 comprise theporous structure 140, and the porous structure 140 is provided on theinner side 102 of the housing walls 120 a, 120 c of the polymer-basedheat pipe 100. Alternatively, the polymer-based housing 110 may comprisea plurality of housing shells, i.e. two or more, that could be assembledtogether to form the polymer-based heat pipe 100.

In one embodiment and referring to FIG. 9, the first and second housingshells 112, 114 may be assembled in a configuration in which the porousstructure 140 formed on each of the first and second housing shells 112,114 face each other. In this configuration, the porous structure 140formed on the first housing shell 112 faces the porous structure 140formed on the second housing shell 114 and the support posts 150maintain a gap within the working fluid chamber 130. The gap between thefirst and second housing shells 112, 114, as such, may be configured asa “vapour core” between the two mating shells, in which the workingfluid 170 can evaporate from one area, channel through the vapour coreand condense back to another area. For example, when the first andsecond housing shells 112, 114 are assembled, the closed polymericchamber may have a height ranging from about 0.25 to about 5 mm.

The polymer-based heat pipe 100 may, for example, and without beinglimitative, have a square shape and centimetric dimension (e.g. 5 cm×5cm×0.1 cm). It will be understood by one skilled in the art that thepolymer-based heat pipe 100 may have different size, dimensions andshape, according to the aimed application. In addition to taking planarshape, the heat pipe can be three-dimensional (3D), with bends andcurvature. In this embodiment, the two or more shells have acorresponding 3D shape so that, when assembled, their inner surfaces arefacing each other to form the vapor core.

According to one embodiment, the working fluid 170 may be water.Alternatively, the working fluid 170 could be, for example, refrigerant(e.g. R134a), ammonia, methanol or acetone. It will be understood thatthe working fluid 170 is selected so as to be compatible with thematerial forming the porous structure 140, and may, accordingly, varyfrom one application to another.

Referring to FIGS. 10 to 13, two other embodiments of a polymer-basedheat transfer device and, more particularly, heat pipes 200, or sectionsthereof, are shown. As in the embodiment described above, thepolymer-based heat pipe 200 comprises a polymer-based housing 210 havinghousing walls 220 a, 220 b, 220 c and 220 d wherein the housing walls200 a-d define a closed working fluid chamber 230. As in theabove-described embodiment, the polymer-based housing 210 has a porousstructure 240. For example, the housing walls 220 a, 220 b, 220 c and220 d may have a thickness ranging from about 0.1 to about 5 mm. Asillustrated, the housing walls 220 a, 220 b, 220 c and 220 d have athickness of about 1 mm. In both embodiments, the porous structure 240extends at least partially in the closed working fluid chamber 230, fromthe housing walls 220 a, 220 c. The polymer-based heat pipe 200 furthercomprises a heat-conductive metal-based foam 260 embedded within thehousing walls 220 a, 220 c. These embodiments can be suitable forapplications that require thermally intensive applications, providinghigher wall thermal conductivity, and structural rigidity. Embeddingheat-conductive metal into the housing walls 220 a-d increases thethermal conductivity of the polymer-based heat pipe 200 making themsuitable for thermally intensive applications while maintaining theadvantages of the polymer-based heat pipes, including their relativelylow costs and light weight. In fact, polymer-based heat pipes includingat least partially embedded heat-conductive metal into the housing walls220 a-d require less metal than metal-based heat pipes.

In a first one of the two embodiments, shown in FIGS. 10 and 11, the twoopposed ones of the housing walls 220 a include heat-conductivemetal-based foam 260 completely embedded within the housing walls 220 a,220 c and acting as a heat-conductive insert. In a second one of the twoembodiments, shown in FIGS. 12 and 13, the heat-conductive metal-basedfoam 260 extends at least partially in the closed working fluid chamber230 and defines the porous structure 240.

Thus, in both embodiments, the heat-conductive metal-based foam 260 isat least partially embedded within the housing walls 220 a, 220 c. Atleast partially embedding heat-conductive material, such asheat-conductive metal-based foam, having a higher heat conductivity thanpolymer, enhances the thermal conductivity of the polymer-based heatpipe 200. Furthermore, if the embedded material is stiffer than thepolymer defining the housing, such as heat-conductive metal-based foam,the at least partially embedded heat-conductive material furtherenhances the structural rigidity of the polymer-based heat pipe 200. Theheat-conductive material can be chosen to have a similar thermalexpansion coefficient as the heat source to which it will be coupled toallow a solid (welded) interface between the heat source and theheat-conductive material. For example, and without being limitative, theheat-conductive material could be: copper, steel, titanium, aluminum,silicon, germanium, superalloys, or any other materials having therequired properties listed above. Alternatively, the housing walls 220a-d can comprise other structural elements to provide more rigidity tothe polymer-based heat pipe 200. For highest rigidity and wall thermalconductivity, solid blocks or sheets of metal or ceramic can be embeddedin the housing walls 220 a-d.

The heat-conductive metal-based foam 260 may be formed from copper foam.Alternatively, the heat-conductive metal-based foam 260 may comprisemetal foam, alloy foam and any other porous materials having therequired porosity and in which may be injected a polymer. It will beunderstood that the heat-conductive metal-based foam 260 is embodied bya material or a combination of material which presents the requiredthermal, electrical and mechanical properties.

The embodiment shown in FIGS. 10 and 11 will now be described in furtherdetails, wherein the porous structure 240 comprises a plurality ofelongated ridges 241, extending substantially parallel to one another,and defining inbetween a plurality of microchannels 242, similar to themicrochannels 140 described above. Thus, the embedded heat-conductivemetal-based foam 260 enhances the thermal conductivity of thepolymer-based heat pipe 200 to enhance heat transfer in the condensationarea and the evaporation area. In addition, it can further increase thestructural rigidity of the polymer-based heat pipe 200. The combinationof elongated ridges 241 and microchannels 242 provides the wickingstructure 240 to the polymer-based heat pipe 200. In an embodimentwherein the wicking structure 240 is not provided by heat-conductivemetal-based foam 260 protruding in the closed working fluid chamber 230,as will be described in more details below, and heat-conductivemetal-based foam 260 is included inside at least some of the walls 220of the polymer-based housing to enhance the thermal conductivity of thepolymer-based heat pipe 200, heat-conductive metal-based foam 260 can beprovided solely in the condensation area and the evaporation area of thepolymer-based heat pipe 200 with the intermediate section, i.e. thesection extending between the condensation area and the evaporation areabeing free of heat-conductive metal-based foam 260 embedded within thehousing.

It is appreciated that, in an alternative embodiment (not shown), theheat-conductive metal-based foam 260 embedded in the housing walls 220a-d can be replaced by other types of heat-conductive metal or ceramicinsert(s) such as, and without being limitative, metal or ceramicparticles to increase the thermal conductivity of the housing walls 220a-d.

In the embodiments wherein the housing walls 220 a-d include at leastpartially embedded heat-conductive metal-based foam 260 (orheat-conductive metal or ceramic), support posts maintaining a gapwithin the working fluid chamber are not compulsory since theheat-conductive metal-based foam 260 (or heat-conductive metal orceramic) increase the structural rigidity of the polymer-based heatpipe. In some implementations, support posts can be provided in theworking fluid chamber 230 in combination with at least partiallyembedded heat-conductive metal-based foam 260 at least partiallyembedded in the housing walls 220 a-d to further enhance the structuralrigidity.

In the embodiment shown in FIGS. 12 and 13, the wicking structure 240 isprovided by a portion of the heat-conductive metal-based foam 260extending in the closed working fluid chamber 230. A portion of theheat-conductive metal-based foam 260 is embedded in the housing walls220 to enhance the thermal conductivity of the polymer-based heat pipe200, and, optionally, the structural rigidity. The portion of theheat-conductive metal-based foam 260 extending in the closed workingfluid chamber 230 has an open porosity to define fluid channels therein,i.e. its pores are not filled with polymer as the portion embeddedwithin the housing wall(s).

In a non-limitative embodiment, the thickness of the heat-conductivemetal-based foam 260 extending in the closed working fluid chamber 230can range between about 0.1 mm and about 1 mm.

Turning now to FIGS. 16 and 17, there are shown two differentimplementations of the polymer-based heat transfer device wherein theheat transfer device is a cold plate. The configuration of the heattransfer device for cold plates is substantially similar to the onedescribed hereinabove in reference to heat pipes, except that coldplates circulate a liquid that collects heat wherein no phase changeoccurs. Furthermore, it requires the addition of inlet and outlet portsto the polymer-based housing, which are operatively connectable to apump and a heat rejection device, such as a radiator. More particularly,when operatively connected to the pump and the heat rejection device,the cold plate is in liquid communication therewith.

Inside the working chamber of the cold plate, the working fluid, i.e.the working liquid, circulates inside a porous structure, which caninclude a plurality of microchannels or a porous material, to collectthe heat. However, as opposed to the heat pipe, it does not usecapillary forces to circulate the fluid since it only contains liquid.Therefore, a cold plate does not include a vapor core.

The microchannels can be provided on one housing wall or a pluralitythereof. In an implementation, the microchannels are provided on theinner surface of one housing wall and the inner surface of the oppositehousing wall is substantially flat (or planar). The ridges defining themicrochannels contact with (or are adjacent to) the flat inner surfaceof the opposite housing wall to cap them and define the microchannelsinbetween. In this implementation, the ridges contacting the oppositehousing wall act as housing wall spacers, similar to the support posts150, to maintain the two opposed ones of the housing walls in aspaced-apart configuration with the working chamber extending inbetween.More particularly, the ridges defining the microchannels extend betweenthe two opposed ones of the housing walls.

As for the above-described heat pipes, in one implementation, the coldplate can also include a heat-conductive porous material, such as ametal-based heat-conductive porous material, at least partially embeddedinto one or more housing walls. In one embodiment, the porous materialcan be embedded in a section of the cold plate housing in contact withor in proximity to the heat source to increase the heat conduction ofthe cold plate. As mentioned above, embedding heat conductive materialinto the housing walls allow heat to efficiently conduct through thewall into the flow.

As for the above-described heat pipes, the working fluid for the coldplate may be water. Alternatively, the working fluid could be, forexample, refrigerant (e.g. R134a), ammonia, methanol, water and ethyleneglycol mixture or acetone. It will be understood that the working fluid170 is selected so as to be compatible with the material forming theporous structure, and may, accordingly, vary from one application toanother.

Referring now to FIG. 16, in a first implementation, the polymer-basedcold plate 400 includes a polymer-based housing 410 having housing walls420 with one of them 420 a having a porous structure 440 providedthereon, on an inner surface 421 thereof. As for the above-describedheat pipes, the inner surfaces 421 of the housing walls 420 define aworking fluid chamber 430. In the illustrated variant, only one 420 a ofthe housing walls 420 includes a porous structure 440. In alternativeembodiments (not shown), more than one of the housing walls 420 can havea porous structure. The porous structure 440 is located inside theworking fluid chamber 430.

The housing 410 of the polymer-based cold plate 400 includes a workingliquid inlet and outlet ports 480, 482 allowing introduction andwithdrawal of the working liquid in and from the working fluid chamber430. In the embodiment shown, the working liquid inlet and outlet ports480, 482 are located on the housing walls 420 opposed to the one 420 aprovided with the porous structure 440, at opposed ends thereof.However, it is appreciated that the configuration of the liquid inletand outlet ports 480, 482 can vary from the embodiment shown in FIG. 16.

As mentioned above, the liquid inlet and outlet ports 480, 482 areoperatively connectable to a pump to allow liquid circulation and to aheat rejection device to be in liquid communication therewith.

In the embodiment shown in FIG. 16, the porous structure 440 includes aplurality of elongated ridges (or fins), extending substantiallyparallel to one another and protruding in the working fluid chamber 430from the housing walls 420 a and defining inbetween a plurality ofmicrochannels 442 (or elongated grooves) through which the liquid cancirculate.

As for the heat pipes, the size, shape and aspect ratio of the porousstructure can vary. Similar embodiments to the ones describedhereinabove in reference to the heat pipes can be foreseen.

In the embodiment shown in FIG. 16, the polymer-based cold plate 400also includes one or a plurality of heat-conductive insert 490 embeddedwith one 420 a of the housing walls 420. In the embodiment shown, theheat-conductive insert 490 is a metal-based or silicon-based plateinserted and contained into the housing wall 420 a, extending below theporous structure 440, i.e. substantially aligned therewith. As mentionedabove, the heat-conductive insert 490 enhances the heat conductiveproperties of the polymer-based housing 410.

However, in alternative embodiments, it is appreciated that thepolymer-based cold plate 400 can be free of the heat-conductive insert.Alternatively, the polymer-based cold plate 400 can include more thanone heat-conductive insert. Furthermore, the position and/orconfiguration of the heat-conductive insert can vary from the embodimentshown. For instance, it does not necessarily extend below the porousstructure 440 or it is not necessarily substantially aligned therewith.

As for the porous structure 140, the porous structure 440 may be formeddirectly onto the housing wall 420. Alternatively, the porous structure440 could be progressively added (such as by additive manufacturing) ormounted onto the housing wall 420. The microchannels can be etched ormachined on the inner surface 421 of the housing walls 420 to create anenhanced heat exchange surface with the working fluid. In this case, themicrochannels and housing walls are one single piece.

As for the heat pipes, in the non-limitative embodiment shown, thehousing 410 includes a first housing shell 412 and a second housingshell 414 superposed to one another and sealed together, with thehousing shell 414 including the porous structure 440 on an inner side402 thereof. Alternatively, the polymer-based housing 410 may comprise aplurality of housing shells, i.e. two or more, that could be assembledtogether to form the polymer-based cold plate 400.

The size, shape, and configuration of the shells 412, 414, fluid chamber430, and the elongated microchannels 442 can be similar to the onesdescribed above in reference to the heat pipes.

Turning now to FIG. 17, a second implementation of a polymer-based coldplate 500 will be described. The polymer-based cold plate 500 issubstantially similar to the polymer-based cold plate 400 describedhereinabove in reference to FIG. 16, except that the combination ofheat-conductive insert 490 and porous structure 440 including aplurality of elongated microchannels 442 is replaced by a porousmaterial partially embedded in one 520 a of the walls 520 of thepolymer-based housing 510. The porous material has a portion protrudingfrom an inner surface 521 of the housing wall 520 a and into the workingfluid chamber 530. The portion of the porous material protruding in theworking fluid chamber 530 defines the porous structure 540, which has anopen porosity to define fluid channels therein, i.e. its pores are notfilled with polymer as in the portion embedded within the housingwall(s).

In the implementation shown, the porous material comprises aheat-conductive metal-based foam 560 embedded within the housing wall520 a. As for the heat pipes, embedding heat-conductive metal into thehousing walls 220 a increases the thermal conductivity and thestructural properties of the polymer-based cold plates 500.

The heat-conductive metal-based foam 560 can contact with (or areadjacent to) the flat inner surface of the opposite housing wall to actas housing wall spacers, similar to the support posts 150, to maintainthe two opposed ones of the housing walls in a spaced-apartconfiguration with the working chamber extending inbetween.

As for the heat pipes, the heat-conductive material for the cold plate500 can be chosen to have a similar thermal expansion coefficient to theheat source to which it will be coupled to allow a solid (welded)interface between the heat source and the heat-conductive material. Theheat-conductive material for the cold plate can be similar to thoseenumerated above in reference to the heat pipes. For example, andwithout being limitative, the heat-conductive material could be: copper,steel, titanium, aluminum, silicon, germanium, superalloys, or any othermaterials having the required properties listed above. Alternatively,the housing walls 520 can comprise other structural elements to providemore rigidity to the polymer-based cold plate 500. For highest rigidityand wall thermal conductivity, rigid and heat-conductive inserts, suchas insert 490, can be embedded in the housing walls 520.

As for the embodiment of the cold plate described hereinabove inreference to FIG. 16, the cold plate of FIG. 17 includes a polymer-basedhousing 510 made of two shells 512, 514, one of them including workingliquid inlet and outlet ports 580, 582 operatively connectable to a pumpand a heat rejection device (not shown).

According to one embodiment, the hermeticity of the polymer-based heattransfer devices, either a heat pipe, a cold plate or a vapor chamber,as described in the present description may be ensured by decreasing thevapour transmission rate (WVTR). For example, the WVTR can be decreasedby adding a high barrier coating layer comprising a single layer or amultilayer film. For example, and without being limitative, the highbarrier coating layer may be formed from or comprise indium tin oxide(ITO). Optionally, ITO may be deposited using plasma-enhanced chemicalvapor deposition (PECVD). Yet optionally, an inorganic layer may furtherbe deposited on the ITO. For example, an aluminum oxide (Al₂O₃) layercan be deposited by atomic layer deposition (ALD). Yet optionally, aprotective layer may further be deposited using PECVD. For example, andwithout being limitative, SiO_(x) or SiN_(x) can be deposited usingPECVD to act as the protective layer. The aluminum oxide (Al₂O₃) layercan also be protected from direct contact with water by 10 to 40 micronscopper deposited by electroplating. The electroplated copper can alsoprotect thin and brittle aluminum oxide (Al₂O₃) layer in the multi-filmagainst stresses caused by CTE mismatch.

In one embodiment, the three layers (organic, inorganic and protectivelayers) that have been previously described could be deposited directlyon a surface of the HDPE. In this configuration, the organic sublayer(e.g. ITO) may be useful to reduce the coefficient of thermal expansionmismatch between HDPE substrate and the inorganic layer to be deposited.The inorganic layer (e.g. Al₂O₃), acting as a barrier layer, can reactwith water and generate non-condensable gases, so a protective layer isrequired to prevent the direct contact of water with Al₂O₃.

According to one embodiment, the high barrier coating layer may bedeposited on a surface of the porous structure, meaning that the highbarrier coating layer may be comprised inside of the polymer-based heattransfer device. Alternatively, for example, when the heat-conductivemetal-based foam defines the porous structure, the high barrier coatinglayer may be deposited on an outside surface of the polymer-based heattransfer device.

According to one embodiment, at least a portion of one inner surface ofthe housing walls is hydrophilic. In the embodiments wherein the porousstructure is defined by a combination of elongated ridges andmicrochannels, a top portion of the porous structure may be hydrophobic.Yet optionally, a bottom portion of the porous structure, such as abottom portion of the microchannels, may be hydrophilic to promote fluidflow between the condensation area and the evaporation area or betweenthe working fluid inlet and outlet ports. For instance, and withoutbeing limitative, a polymeric surface can be made hydrophilic by plasmatreatment of the exposed inner surfaces of the housing walls (either thepolymer of the polymer-based heat transfer device or a metal coatingapplied thereon).

A metal coating can be applied on at least a portion of the innersurfaces of the housing walls to enhance the hydrophilicity and/or thegas barrier properties. For instance, a thin metal film of 10 to 40microns, such as copper or chrome, can cover at least a portion thereof.

According to one embodiment, the first and second housing shells aresealed along their perimeter. Optionally, the first and second housingshells can be bonded together using ultrasonic plastic welding toproduce hermetic joints. Alternatively, and without being limitative,laser plastic welding and high vacuum epoxies can be used for bondingthe first housing shell with the second housing shell. Alternatively,ultrasonic metal welding can also be used to bond the first metalizedpolymeric housing shell with the second housing shell to create hermeticjoints.

In accordance with another aspect, a process for manufacturing apolymer-based heat transfer device as the one described in the presentdescription is provided.

Generally described, the manufacturing process for manufacturing thepolymer-based heat transfer device comprises the steps of: forming afirst polymer-based housing shell and a second polymer-based housingshell; superposing the first housing shell and the second housing shell;at least partially peripherally sealing the first housing shell and thesecond housing shells together; and inserting a working fluid inside theworking fluid chamber. The porous structures manufactured from thisprocess can be tailored and adapted, which may help to adapt the use ofthe polymer-based heat, as presented in the previous description, to thespecifications encountered by one skilled in the art, such as: the heatflux patterns expected from the heat source, as well as tailoring of thecapillary forces according to the pressure drop in the porous structurein case of a heat pipe. This process also allows to manufacture apolymer-based heat transfer device comprising a piece of conductiveporous material such as copper metal foam to enhance its heat transferproperties.

In one embodiment, the manufacturing process may use plastic fabricationmethods, such as, but without being limited to: injection molding,stamping and/or additive manufacturing such as tridimensional printing(3D printing) to form a polymer-based housing or, alternatively, eachone of the first and second housing shells. As mentioned above,microchannels can be etched or machined on an inner side of one or morehousing walls to create an enhanced heat exchange surface with theworking fluid.

In one embodiment, an aluminum mold may be injected with melted plastic(e.g. polymer) so as to reproduce tridimensional structures (such as aporous structure and/or a curved or bent heat transfer device geometry)having various shapes, dimensions, size and aspect ratio on the housingwall of the polymer-based heat transfer device. The use of an injectingmethod advantageously allows to create almost any pattern, shape ordistribution with a reproducible process.

In regard to the step of forming a first polymer-based housing shell anda second polymer-based housing shell, it may comprise the step offorming a porous structure on at least one inner surface of the firstand second inner shells. For example, the forming step may comprise thestep of injecting plastic/polymer in a mold. Optionally, a metal foammay be placed in the mold prior to the polymer injection. The injectedliquid polymer will enter into the pores of the foam, partially orcompletely through its thickness. When the polymer completely fills thefoam pores through its entire thickness, the metal foam becomes embeddedinto the housing wall(s), as described above, for increased thermalconductivity and/or mechanical strength. When only part of the foamthickness is filled by the injected liquid plastic/polymer, thethickness filled with the polymer will be embedded in the housingwall(s) for increased thermal conductivity and/or mechanical strength,whereas the thickness that is not filled by the polymer will provide theporous structure. This non-filled side will face the inside of the heattransfer device, facing the opposing shell. Metal foam is typically usedwhen one is required to manufacture a polymer-based heat transfer devicefor applications that require higher wall thermal conductivity andstructural rigidity, as it has been previously presented. Suchconfiguration could also be used for high heat transfer rateapplications that require higher evaporation and porous rates. Otheralternatives to the injection molding methods comprise, but are notlimited to, stamping, 3D printing, additive method, subtractive method,or any other method allowing to create patterns onto the first and/orsecond polymer-based housing shells.

In regard to the step of superposing the first housing shell and thesecond housing shell, it may comprise assembling the first and secondhousing shells with the surfaces facing one another. The step ofsuperposing the first and second housing shells may further comprise thestep of maintaining a gap between the two surfaces, so that they remainspaced-apart and define a working fluid chamber for the vapor. In caseof a cold plate, superposing the first and second housing shells mayfurther comprise the step of juxtaposing, and even contacting, a topsurface of ridges protruding from an inner surface of one of the housingshells to an inner surface of an opposed one of the housing shells.Optionally, the steps of superposing and assembling the first and secondhousing shells may further comprise the step of aligning the firsthousing shell with the second housing shell. The step of aligning thefirst and second housing shells may comprise marking at least one of thefirst and second housing shells with a marking means selected from thegroup consisting of a pen, a laser, an engraving, an etching, a print, acarving, a molded protrusion or recess, a laser, an illumining deviceand a projection. As it will be readily understood, the marking meanscomprise but are not limited to methods and/or means of physically,superficially and/or temporarily/permanently marking the first andsecond housing shells so as to facilitate their alignment during theassembling step.

In regard to the step of peripherally sealing the first housing shelland the second housing shell, it may comprise the step of bonding thefirst and second housing shells together using ultrasonic plasticwelding, ultrasonic metal welding, laser plastic welding, thermoforming,glue, high vacuum epoxies or any other methods and/or allowing toperipherally seal the first and second housing shells together.

In one embodiment, the step of peripherally sealing the first and secondhousing shells may comprise the step of removing gas, such as air and/orany other non-condensable gases, from the working fluid chamber.

In regard to the step of inserting the working fluid inside the workingfluid chamber, for a heat pipe, it may comprise the step of using andinserting a small tube into an injection hole provided on one side ofthe polymer-based heat transfer device or in a trench formed through thejoint between the two shells. Optionally, the small tube can be cutafter injecting the working fluid within the closed working fluidchamber. Yet optionally, the injection hole may be sealed to avoid theworking fluid from leaking from the sealed polymer-based-heat transferdevice.

According to one embodiment, for a heat pipe, the step of inserting theworking fluid inside the working fluid chamber may comprise a step ofcreating a vacuum in the polymer-based heat transfer device.

According to one possible embodiment, for a heat pipe, the step ofsealing the injection hole may comprise the step of adding a sealant, amelted drop, a plastic joint, silicone, any polysiloxane-basedcompounds, cold welding using a pinch-off tool, combination thereof, orany other material allowing to seal the injection hole.

According to one possible embodiment, the process may further comprise astep of applying a coating on the inside surface of the polymer-basedheat transfer device for impermeability and/or hydrophilicity of theinner surfaces. Optionally, the coating can act as a high barriercoating layer and can help enhance the hermeticity of the polymer-basedheat transfer device. Alternatively or in addition, the high barriercoating layer can be applied on an outside surface of the polymer-basedheat transfer device.

According to one possible embodiment, the process may further comprise astep of treating an internal surface of the polymer-based heat transferdevice with a plasma treatment to increase the hydrophilicity propertyof the surface. Alternatively, the hydrophilicity of a portion or anentirety of an interior surface of the polymer-based heat transferdevice may be increased by adding hydrophilic coatings.

According to one possible embodiment and as shown on FIG. 18, theprocess may comprise a step of electroplating a metal layer onto asurface of the polymer-based heat transfer device. Optionally, a metalseed layer including chrome and copper may be deposited on the housingwalls of the polymer-based heat transfer device prior to the step ofelectroplating the metal layer. Yet optionally, the metal seed layer maybe deposited by physical vapor deposition (PVD) method. A copperelectroplating may then be employed to deposit a copper layer on theinner surface of the heat transfer device. This step is aimed at makingthe surface of the housing walls hydrophilic, and increasing the gasbarrier properties. Optionally, and if the polymer-based heat transferdevice is required to have a better hermeticity, the step ofelectroplating the surface of the polymer-based heat transfer device mayfurther comprise the step of adding thin layers of high barrierplastics. Optionally, the plastic may be ethylene vinyl alcohol (EVOH).Alternatively, the plastic could be any ethylene and/or vinylalcohol-based polymer having the required hydrophilicity properties.Optionally, the metal layer and the plastic layer may be bonded togetherusing a laser, ultrasonic treatment or an epoxy to produce hermeticjoints.

According to one possible embodiment, the process may comprise a step oftreating a portion or an entirety of a surface of the housing wallsand/or the porous structure with a plasma for reducing the workingliquid contact angle. For example, the surface may be treated with anoxygen plasma so as to reduce the contact angle of the water on the HDPEsurface, as shown in FIG. 19. In another example, the hydrophiliccoating is created by attaching chemical molecules on the surface as aself-assembled monolayer (SAM), such as APTES or other organosilanes.

According to one possible embodiment for a heat pipe shown on FIG. 20,the steps of creating the vacuum and inserting the working fluid can beachieved with an integrated charging station. For example, the chargingmay allow to insert precise amounts of the working fluid (e.g. 2 to 2.5mL) and creating a vacuum up to approximately 1 mTorr. In the embodimentshown, the charging station includes, amongst others, a flow meter 692,a vacuum gauge 694, a vacuum pump 696, a heat pipe connection 698, and aliquid trap 699.

According to one possible embodiment illustrated on FIG. 21, thepolymer-based heat transfer device 700 as described in the presentdescription may be used in batteries 786 for electric or hybridvehicles, for example for extracting heat from Li-ion batteries 786. Inthe embodiment shown, the heat transfer device 700 is a heat pipe.However, in an alternative embodiment (not shown), it could be a coldplate including a housing with working fluid inlet and outlet ports.

According to one possible embodiment illustrated on FIG. 22, thepolymer-based heat transfer device 700 as described in the presentdescription may also be used in prosthesis systems, for example forejecting metabolic heat out of a body portion.

In summary, the polymer-based heat transfer devices described above canbe advantageous over prior art heat transfer devices for theirperformance, relatively low cost, and light weight. On a general aspect,they are compatible with a broad variety of electronic packaging methodsand are electrically insulating.

The polymer-based heat transfer devices described above can be alsoadvantageous for a manufacturer, since the production of thepolymer-based heat transfer devices as defined in the presentdescription relies on more flexible fabrication methods, hence allowingthe formation of various shape factors according to one's needs.

The manufacturing process described above can be used to directly formthe plastic casing or electrical/electronic equipment, machines or otherproducts that benefit from enhanced cooling and heat removal. Theproduct casing with embedded heat transfer device would substantiallyefficiently distribute the heat from the internal heat source to theentire or a large portion of the outer surface of the product. This willhelp reject heat to the ambient air and reduce the temperature of theproduct.

Several alternative embodiments and examples have been described andillustrated herein. The embodiments of the invention described above areintended to be exemplary only. A person skilled in the art wouldappreciate the features of the individual embodiments, and the possiblecombinations and variations of the components. A person skilled in theart would further appreciate that any of the embodiments could beprovided in any combination with the other embodiments disclosed herein.It is understood that the invention may be embodied in other specificforms without departing from the central characteristics thereof. Thepresent examples and embodiments, therefore, are to be considered in allrespects as illustrative and not restrictive, and the invention is notto be limited to the details given herein. Accordingly, while specificembodiments have been illustrated and described, numerous modificationscome to mind without significantly departing from the scope of theinvention as defined in the appended claims.

1. A polymer-based heat transfer device comprising: a polymer-basedhousing having housing walls with an inner surface defining a workingfluid chamber, a porous structure extending in the working fluid chamberfrom at least one of the housing walls, and a plurality of housing wallspacers extending between two opposed ones of the housing walls tomaintain the two opposed ones of the housing walls in a spaced-apartconfiguration with the working fluid chamber extending in between. 2.The polymer-based heat transfer device according to claim 1, wherein thepolymer-based housing comprises a first housing shell and a secondhousing shell superposed to one another and sealed together and thepolymer-based heat transfer device further comprises a high barriercoating applied onto at least one of the inner surface of the housingwalls and an outer surface of the housing walls.
 3. The polymer-basedheat transfer device according to claim 1, wherein the plurality ofhousing wall spacers comprises a plurality of spaced-apart support postsprotruding from the inner surface of one of the housing walls towards anopposed one of the housing walls and contacting same.
 4. Thepolymer-based heat transfer device according to claim 1, wherein theporous structure comprises a plurality of spaced-apart ridges protrudingfrom at least one of the housing walls and extending substantiallyparallel to one another and defining inbetween a plurality ofmicrochannels.
 5. The polymer-based heat transfer device according toclaim 4, wherein the plurality of housing wall spacers comprises theridges which extend towards an opposed one of the housing walls andcontact same.
 6. The polymer-based heat transfer device according toclaim 4, wherein the ridges are polymer-based ridges.
 7. Thepolymer-based heat transfer device according to claim 4, wherein abottom surface of the microchannels is hydrophilic and a top surface ofthe microchannels is hydrophobic.
 8. The polymer-based heat transferdevice according to claim 1, wherein the polymer-based heat transferdevice is a heat pipe and the working fluid chamber is a closed workingfluid chamber.
 9. The polymer-based heat transfer device according toclaim 1, wherein the polymer-based heat transfer device is a cold plateand the polymer-based housing comprises a working fluid inlet port and aworking fluid outlet port, spaced-apart from the working fluid inletport.
 10. The polymer-based heat transfer device according to claim 1,wherein the polymer-based housing comprises at least one heat-conductiveinsert embedded within at least one of the housing walls.
 11. Thepolymer-based heat transfer device according to claim 10, wherein the atleast one heat-conductive insert comprises a heat-conductive metal-basedfoam entirely embedded in the at least one of the housing walls and theporous structure comprises a plurality of spaced-apart ridges protrudingfrom at least one of the housing walls and extending substantiallyparallel to one another and defining inbetween a plurality ofmicrochannels.
 12. A polymer-based heat transfer device comprising: apolymer-based housing having housing walls defining a working fluidchamber and a porous structure extending in the working fluid chamberfrom at least one of the housing walls; and a heat-conductivemetal-based foam contacting the at least one of the housing walls. 13.The polymer-based heat transfer device according to claim 12, whereinthe heat-conductive metal-based foam at least partially extends in theworking fluid chamber to define the porous structure.
 14. Thepolymer-based heat transfer device according to claim 12, wherein theheat-conductive metal-based foam is entirely embedded in the at leastone of the housing walls and the polymer-based housing comprises a firsthousing shell and a second housing shell superposed to one another andsealed together.
 15. The polymer-based heat transfer device according toclaim 12, wherein the polymer-based housing further comprises aplurality of housing wall spacers including a plurality of spaced-apartsupport posts protruding from an inner surface of one of the housingwalls towards an opposed one of the housing walls and contacting same.16. The polymer-based heat transfer device according to claim 14,wherein the porous structure comprises a plurality of spaced-apartridges protruding from at least one of the housing walls and extendingsubstantially parallel to one another and defining inbetween a pluralityof microchannels.
 17. The polymer-based heat transfer device accordingto claim 16, wherein the ridges extend towards an opposed one of thehousing walls and contact same to define housing wall spacers.
 18. Aprocess for manufacturing a polymer-based heat transfer device, theprocess comprising: forming a first polymer-based housing shell and asecond polymer-based housing shell, at least one of the polymer-basedhousing shells having a porous structure on at least one inner surfacethereof; superposing the first housing shell and the second housingshell with the inner surfaces facing another one of the inner surfacesand being spaced-apart to define a working fluid chamber inbetween; atleast partially peripherally sealing the first housing shell and thesecond housing shells together; and inserting a working fluid inside theworking fluid chamber.
 19. The process according to claim 18, whereinforming the first polymer-based housing shell and the secondpolymer-based housing shell comprises forming a plurality of housingwall spacers on an inner surface of at least one of the first and thesecond polymer-based housing shells, the housing wall spacers beingconfigured to contact an opposed one of the inner surface when the firstand the second polymer-based housing shells are superposed.
 20. Theprocess according to claim 18, wherein forming the first polymer-basedhousing shell and the second polymer-based housing shell comprisesforming a plurality of spaced-apart ridges protruding from an innersurface of at least one of the housing shells and extendingsubstantially parallel to one another and defining inbetween a pluralityof microchannels.
 21. The process according to claim 18, wherein formingthe first polymer-based housing shell and the second polymer-basedhousing shell comprises embedding at least one heat-conductive insertwithin at least one of the first and the second polymer-based housingshells.